1. Field of the Invention
The present invention relates to a pressure control valve. Further, the present invention relates an evaporation fuel discharge control device which, when fuel is supplied to a fuel tank of a car, is used to control the discharge of evaporation fuel from the fuel tank.
The present application is based on Japanese Patent Applications No. Hei. 10-106055 and 11-59674 which are incorporated herein by reference.
2. Description of the Related Art
Generally, in a car, evaporation fuel from a fuel tank is temporarily stored in a canister through an evapo-pipe, and is then introduced into an engine at a suitable time. A pressure-control valve is disposed in the evapo-pipe.
And, conventionally, as a pressure control valve which is used in such pipe, for example, there is known a pressure control valve which is disclosed in Japanese Utility Model Publication No. Hei. 1-83976.
FIG. 17 shows the pressure control valve that is disclosed in the above-cited publication. That is, the pressure control valve comprises a cap 202 which includes a first port 201 in communication with a fuel tank, and a body 204 including a second port 203 in communication with a canister.
The body 204 includes a partition wall 205 in the interior portion thereof; and, in particular, between the upper surface of the partition wall 205 and the inner surface of the cap 202, there is interposed a first valve 206, and, inside the first valve 206, in particular, between the upper surface of the partition wall 205 and a valve body 207, there is interposed a second valve 208.
And, in the portion of the partition wall 205 that is situated on the inner side of the second valve 208, there is formed a fluid passage 209.
However, in the above-structured conventional pressure control valve, since the fluid passage 209 is formed only in the portion of the partition wall 205 that is situated on the inner side of the second valve 208, when the pressure within the fuel tank increases suddenly, it is difficult to introduce the evaporation fuel within the fuel tank through the first and second ports 201 and 203 to the canister side quickly.
Further, as an evaporation fuel discharge control device which, when fuel is supplied to a fuel tank of a car, is used to control the discharge of evaporation fuel from the fuel tank, for example, there is known a device which is disclosed in Japanese Patent Publication No. Hei. 8-189423.
Now, FIG. 18 shows the evaporation fuel discharge control device disclosed in the above-cited patent publication. In this evaporation fuel discharge control device, a tank main body 302 of a fuel tank 301 is connected to a canister 303 through an evaporation fuel passage 304.
Within the tank main body 302, there is disclosed a float valve 306 which is used to close an entrance portion 305 of the evaporation fuel passage 304 when fuel within the tank main body 302 exceeds a given liquid level.
And, in the evaporation fuel passage 304, there is disposed a switch valve assembly 307.
The switch valve assembly 307 has a diaphragm valve which divides a positive pressure chamber 307a and a back pressure chamber 307b, while the evaporation fuel passage 304 includes the positive pressure chamber 307a. 
And, when the pressure on the positive pressure chamber 307a side is higher by a predetermined value or more than the pressure on the back pressure chamber 307b side, the evaporation fuel passage 304 is opened.
On the back pressure chamber 307b side of the switch valve assembly 307, there is opened a pressure introduction passage 309 which is connected to an entrance portion 308a of a fuel supply pipe 308.
And, the portion of the evaporation fuel passage 304 on the upstream side of the switch valve assembly 307 is connected to the pressure introduction passage 309 by a communicating passage 310.
In the communicating passage 310, there is disposed a check valve 311 which is structured such that it can be opened when the pressure on the upstream side of the switch valve assembly 307 is higher by a given value or more than the pressure on the pressure introduction passage 309 side.
In the evaporation fuel discharge control device of this type, if a cap (not shown) of the fuel supply pipe is removed when starting fuel supply, then the pressure on the back pressure chamber 307b side of the switch valve assembly 307 is reduced down by the predetermined value or more than the pressure on the positive pressure chamber 307a side of the switch valve assembly 307 through the pressure introduction passage 309 to thereby open the switch valve assembly 307, so that the evaporation fuel from the tank main body 302 is fed through the evaporation fuel passage 304 and is stored to the canister 303.
And, if the internal pressure of the tank main body 302 is increased due to start of the fuel supply and the upstream side pressure of the switch valve assembly 307 is thereby increased by the given value or more than the pressure on the pressure introduction passage 309 of the check valve 311, then the check valve 311, which is disposed in the communicating passage 310, is caused to open. As a result of this, a part of the evaporation fuel within the tank main body 302 is introduced through the pressure introduction passage 309 into the entrance portion 308a of the fuel supply pipe 308 and is then returned back into the tank main body 302 together with fuel which is supplied from a fuel supply gun 312.
And, if the tank main body 302 is filled with fuel, then the entrance portion 305 of the evaporation fuel passage 304 is closed by the float valve 306, with the result that the pressure on the upstream side of the switch valve assembly 307 with the communication thereof with respect to the interior portion of the tank main body 302 cut off is caused to decrease quickly to thereby close the switch valve assembly 307 and check valve 311.
And, if the cap (not shown) is mounted on the fuel supply pipe 308 after completion of the fuel supply, then the pressure of the entrance portion 308a of the fuel supply pipe 308 increases together with and equally to the pressure of the interior portion of the tank main body 302, so that the pressure on the back pressure chamber 307b side of the switch valve assembly 307 is caused to increase through the pressure introduction passage 309 and the pressure of the check valve 311 on the pressure introduction passage 309 side thereof is also caused to increase.
However, in the above-mentioned conventional evaporation fuel discharge control device, because, if the interior portion of the tank main body 302 is filled with the fuel, then not only the entrance portion 305 of the evaporation fuel passage 304 is closed by the float valve 306 but also the switch valve assembly 307 and check valve 311 are closed, the pressure on the upstream side of the switch valve assembly 307 remains as pressure equivalent to the atmospheric pressure, which causes the float valve 306 to stick to the entrance portion 305 of the evaporation fuel passage 304.
Therefore, conventionally, in order to prevent the float valve 306 from sticking to the entrance portion 305 of the evaporation fuel passage 304, for example, the float valve 306 is divided in two upper and lower stages. However, in this case, there arise other problems: that is, the float valve 306 is complicated in structure, the manufacturing cost thereof is increased, and the response property thereof is lowered.
The present invention aims at the above-mentioned problems found in the conventional pressure control valve. Accordingly, it is an object of the invention to provide a pressure control valve which, when the pressure on the first port side increases suddenly, can flow a large quantity of fluid to the second port side.
It is another object of the invention to provide an evaporation fuel discharge control device which is able to prevent easily and positively a float valve from sticking to the entrance portion of an evaporation fuel passage.
In attaining the above objects, according to a first aspect of the present invention, there is provided a pressure control valve. In the pressure control valve, a casing has a first port formed on a first side of the casing, a second port formed on a second side. A positive pressure valve is disposed in the casing, the positive pressure valve moving to a side of the second port to thereby communicating with the side of the second port when a pressure on a side of the first port becomes higher than the side of the second port. A negative pressure valve is disposed in the casing, the negative pressure valve moving to the side of the first port to thereby communicating with the side of the second port when the pressure on the side of the first port becomes lower than the side of the second port. Further, flow passage expanding means is provided which, when the positive pressure valve has moved to the side of the second port beyond a given distance, allows the side of the first port to communicate with the side of the second port by opening the negative pressure valve.
Preferably, the positive pressure valve is formed as a cylindrical-shaped bottomed valve having an opening on the bottom of the first port. The negative pressure valve has a rod portion extending through a bottom surface portion of the positive pressure valve, a valve portion stored within the positive pressure valve and connected to a first end of the rod portion, and an energizing portion connected to a second end of the rod portion for energizing the rod portion to the side of the second port. Further, on the side of the second port of the casing, a projecting portion is formed which, when the positive pressure valve has moved to the side of the second port beyond a given distance, can be contacted with the energizing portion of the negative pressure valve to thereby allow the negative pressure valve to communicate with the side of the second port.
Further, the first port can be connected to a fuel tank, whereas the second port can be connected to a canister.
In the above pressure control valve, if the pressure on the first port side increases suddenly, then the positive pressure valve is moved to the second port side beyond a given distance to thereby allow the negative pressure valve to communicate with the second port side, so that the fluid or fuel from the first port side is allowed to flow to the second port through the respective flow passages of the positive and negative pressure valves.
Also, if the pressure on the first port side increases suddenly, then the positive pressure valve is moved to the second port side together with the negative pressure valve, and, when the positive pressure valve has moved to the second port side beyond a given distance, the projecting portion formed in the casing is contacted with the energizing portion of the negative pressure valve to thereby allow the negative pressure valve to communicate with the second port side.
In attaining the above objects, according to a second aspect of the present invention, there is provided an evaporation fuel discharge control device. A canister for adsorbing evaporation fuel from a fuel tank has a tank main body with a fuel supply pipe, an evaporation fuel passage for connecting the tank main body and the canister, and a float valve is disposed within the tank main body for closing an entrance portion of the evaporation fuel passage when fuel within the tank main body exceeds a given liquid level. Further, a switch valve includes a positive pressure chamber and a back pressure chamber, the evaporation fuel passage being disposed on a side of the positive pressure chamber, and the switch valve is structured such that it can be opened when a pressure on the side of the positive pressure chamber is higher by a predetermined value or more than a pressure on a side of the back pressure chamber. A pressure introduction passage for connecting an entrance portion of the fuel supply pipe to the back pressure chamber of the switch valve is provided. First communicating means allows an upstream side of the switch valve to communicate with the pressure introduction passage when a pressure on the upstream side of the switch valve is higher by a given value or more than a pressure on a side of the pressure introduction passage. Second communicating means allows the upstream side of the switch valve to communicate with the pressure introduction passage when the pressure on the side of the pressure introduction passage is higher by a given value or more than the pressure on the upstream side of the switch valve.
Preferably, the first and second communicating means include a positive pressure valve and a negative pressure valve to be stored within a valve chamber which is formed integrally with the switch valve, and the negative pressure valve is disposed in the positive pressure valve.
Preferably, the evaporation fuel discharge control device further includes passage expansion means disposed so as to be opposed to the pressure introduction passage and capable of opening the negative pressure valve when the positive pressure valve is moved beyond a given distance toward an opening of the pressure introduction passage, the opening of the pressure introduction passage being opened in the valve chamber.
In an evaporation fuel discharge control device according to the invention, on completion of fuel supply, if the cap is mounted on the fuel supply pipe, then the pressure of the entrance portion of the fuel supply pipe increases up to the same level as the pressure within the tank main body, and thus the second communicating means is opened through the pressure introduction passage to thereby increase the pressure on the upstream side of the switch valve up to almost the same level as the pressure within the tank main body, thereby removing the sticking of the float valve to the entrance portion of an evaporation fuel passage.
Also, in an evaporation fuel discharge control device, the positive pressure valve of the first communicating means and the negative pressure valve of the second communicating means are stored within the valve chamber which is formed integrally with the switch valve, and the negative pressure valve is disposed in the positive pressure valve.
Further, if the positive pressure valve is moved, due to the high pressure used in the high flow rate of fuel supply, beyond a given distance toward the opening side of the pressure introduction passage which is opened in the valve chamber, then the negative pressure valve can be opened and the area of the passage toward the pressure introduction passage can be expanded by the passage expanding means.
Features and advantages of the invention will be evident from the following detailed description of the preferred embodiments described in conjunction with attached drawings.